The invention relates to fluorescence spectrophotometric equipment and methods, particularly for making high-precision measurements in the determination of specimen response to a chemical, biological or physical agent wherein evaluation is made for a "control" sample of the specimen in relation to an "experimental" sample of the specimen.
U.S. Pat. Nos. 4,795,256 and 5,039,219 are illustrative of state-of-the-art precision fluorescence spectrophotometric equipment in which instrument sensitivity (e.g., as defined by signal/noise ratio) is high and cuvette-based fluorescence experiments are conventionally made, using one sample at a time. However, high-precision measurements do not necessarily yield meaningful and accurate results, particularly when one is concerned with the accuracy with which weak external influences on real-time kinetics of samples of biological cells are to be determined by fluorimetry. The accuracy of any experimental evaluation is limited by repeatability, that is, the extent to which a measurement with the same initial conditions (e.g., including the same biological state of the sample) will produce the same result. For example, when data from two or more consecutive fluorescence recordings (i.e., "experimental" and "control") are compared, it is generally assumed that the quantitative biological response patterns (i.e., kinetics) are the same. However, this may not always be the case, in that the false assumption of a constant cell response will be reflected in erroneously interpreted results. In other words, two separate recordings will differ, not because of imprecise measurements, but because the response kinetics may have changed in one or more significant ways. If a change in response kinetics is not accounted for, the change will factor into a measured fluorescence change, consequently prompting an inaccurate interpretation of results.